A 9-year-old girl presents for continuing weight loss of 10 kg over the course of 1 year. Medical history showed three episodes of pneumonia requiring hospital admission in the 6 months before presentation and 4 months of weekly psychotherapy for anorexia nervosa. A thorough history of eating behavior and a review of systems revealed not only typical aspects of prepubertal anorexia nervosa but also vomiting at night while asleep, difficulty drinking liquids, epigastric pain, and a frequent experience of "a lump in the throat"; these symptoms were not suggestive of a diagnosis of anorexia nervosa but rather of esophageal achalasia. The patient was transferred to the Department of Pediatrics, and a diagnosis of esophageal achalasia was made by chest x-ray and barium swallow. After dilatation and botulinum toxin application, the patient regained weight easily and was discharged in stable condition. In this case, esophageal achalasia mimicked prepubertal anorexia nervosa.